Thermal decomposition of silane (SiH4) is an established method for the production of solar cell grade silicon. The decomposition takes place on already existing silicon surfaces, either oil Si rods in a Siemens reactor or on Si particles in a fluidised bed reactor.
As examples of prior art in the field, mention may be made of FR A 2591412, WO A12005/054130 and WO A12005/118474.
Decomposition in a gas phase in a free space reactor is challenging because large parts of the product consist of extremely small Si particles (dust), having a, density of about 50 g/L. This dust has a very large surface/volume ratio, and is subject to oxidation and contamination. The oxide layer makes it difficult to melt the powder.
There is therefore a need for an apparatus and a method with which to compact the powder that do not contaminate the powder or expose it to oxygen.
The aforementioned problem is sought to be solved by an apparatus and a method as respectively disclosed herein.